Complex geometry/textures and such have always run the risk of this kind of thing happening...guess I've just gotten used to the abuse over the years. I remember when they added Abyssea to XI everyone had hissy fits over the frame dips around mobs like the sand worms and raptors---and we had high end hardware running a game that could run on a toaster (so to speak). A lot of times it comes sort of down to a fill rate issue---CPU or RAM bottlenecking mostly. And this game still runs a lot of stuff on the CPU that could and should be offloaded to the GPU.... but that is another issue.

I've pretty much resorted to always turning off a lot of eye candy in games by default. After I play for a while and things seem smooth enough I may go turn some back on to see what I can get away with. Unfortunately, there hasn't been much wiggle room for my laptop with this game. Can try tinkering with some things like Glare and Radial Blur, physics, maybe shadows or grass, LoD cache, etc. to see if you can mitigate some of the slow down--just depends on how much you might need to trim versus how much your eyeballs can tolerate I guess.

You may be able to simulate the problem by going out to East Shroud and running over to Little Solace. Watch your frame rate as you pan back towards the Hawthorne Aetheryte. This tends to be a bit of a problem spot that may prove a good testing spot (instead of trying to compare results in an instanced event). If not there, you may be able to do it in one of the busier cities---possibly by angling your view towards the market places or something (lots of players, lots of AA/AF, wire frames, textures, etc. to process).